Current treatment strategies of psoriasis are not completely satisfactorily. By inhibiting inflammatory cytokines, nicotinamide may enhance the effects of current topical treatments. Preliminary studies have shown that nicotinamide, which is a vitamin B derivative, is effective in the treatment of psoriasis. According to lack of data, we will investigate the beneficial effects of adding nicotinamide to calcipotriol for patients with mild to moderate psoriasis.